You probably already know the 4 seasons but seasons in Korean can go more in-depth than that! Following the Chinese lunar calendar Korea’s traditional calendar has a solar system for seasons too, spaced approx. 15 days apart these dates mark specific points in the seasons.
Since it follows the Chinese calendar it the begins in February instead of January. The names are the original ones pulled from Chinese with matching hanja. The Korean calendar was used until the western Gregorian calendar was adopted in 1896.
Of course, please don’t take this as a clear-cut guide to weather in Korea, it can be close but think of it similar to our calendars which mark the seasons like “Start of Spring” but as you know can feel wildly off haha.